Generator sets (gensets), such as alternating current (AC) gensets, may provide electrical power to loads when power is unavailable from an electric utility or another power source (e.g., a solar generator set, a fuel cell generator set, a wind generator set, etc.). When the utility power returns, the load may be transferred back to the utility. Further, gensets may supplement power of the utility when demand of the load exceeds the supply of the utility and some load is removed from the utility. When adding the gensets to the utility to supplement or transfer loads, a small difference in the frequency, phase, and/or magnitude between the gensets and the utility may create large over-current. Therefore, before adding gensets to supplement or transfer loads, the frequency, phase, and magnitude of the gensets may need to be synchronized to those of the utility to avoid disruption to the loads. Besides synchronization between gensets and utilities, synchronization may be desired among two or more gensets. For example, a group of paralleled gensets may be employed to supply large amount of power and the AC output of each genset may need to be synchronized to one another.